<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form action="/ajax_json/" method="POST" target="ifm1">
    {% csrf_token %}
    <iframe id="ifm1" name="ifm1"></iframe>
    <input type="text" name="username">
    <input type="text" name="email">
    <input type="submit" onclick="sumitForm()" value="提交">
</form>

<script src="/static/jquery-1.12.4.js"></script>
<script>
    function sumitForm() {
        $('#ifm1').load(function () {
            var text =$('#ifm1').contents().find('body').text();
            var obj = JSON.parse(text)
        })
    }
</script>
</body>
</html>